learn programming in c language

Introduction

C language Developed in 1972 in Bell Laboratories.

Purpose is to develop Unix oprating system.

High level language

Extension is .c

Use of C:

Operating system.

Text Editor

DataBase

Modern program

Language compiler

/* This is comment

Is multiline

 */

//single line comment

Simple Program.

#include<stdio.h> 

Int main()

{

Printf(“hello world \n”);

Return 0;

}

DataTypes

Char : for character

int : for integer number

float : for decimal values

double : float * 2

Variable :Name given to memory location

Int   number   =   10 ;

Int	Number	10
DataType	Variable	value

Functions:

Int function();

int main()

{

int i = function();

printf(“value is: %d \n”i);

}

Int function()

{

Return 0;

}

Operator: Symbol that tell compiler to perform specific mathematical or logical operation.

Arithmetic 

Arithmetic Operators:

Operator	Description	Example
+	Adds two operands	A + B will give 30
-	Subtracts second operand from the first	A - B will give -10
*	Multiply both operands	A * B will give 200
/	Divide numerator by denumerator	B / A will give 2
%	Modulus Operator and remainder of after an integer division	B % A will give 0
++	Increment operator, increases integer value by one	A++ will give 11
--	Decrement operator, decreases integer value by one	A-- will give 9

Increment and decrement operators:

Let a=5 and b=10

a++;  //a becomes 6

a--;  //a becomes 5

++a;  //a becomes 6

--a;  //a becomes 5 

Logical Operator:

Operator	Description	Example
&&	Called Logical AND operator. If both the operands are non-zero, then condition becomes true.	(A && B) is false.
||	Called Logical OR Operator. If any of the two operands is non-zero, then condition becomes true.	(A || B) is true.
!	Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true then Logical NOT operator will make false.	!(A && B) is true.

Assignment Operators:

Operator	Example	Same as
=	a=b	a=b
+=	a+=b	a=a+b
-=	a-=b	a=a-b
*=	a*=b	a=a*b
/=	a/=b	a=a/b
%=	a%=b	a=a%b

Relational Operators

Operator	Description	Example
==	Checks if the values of two operands are equal or not, if yes then condition becomes true.	(A == B) is not true.
!=	Checks if the values of two operands are equal or not, if values are not equal then condition becomes true.	(A != B) is true.
>	Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true.	(A > B) is not true.
<	Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true.	(A < B) is true.
>=	Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true.	(A >= B) is not true.
<=	Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true.	(A <= B) is true.

Bitwise Operators:

Operators	Meaning of operators
&	Bitwise AND
|	Bitwise OR
^	Bitwise exclusive OR
~	Bitwise complement
<<	Shift left
>>	Shift right

Programs : 

Write a program to calculate area of rectangle use #define preprocessor?

#include<stdio.h>

#define length 10

#define width 5

Void  main()

{

Int area;

Area=length * width;

Printf(“value of area is %d”,area);

}

Write a program to swap two numbers?

#include <stdio.h>

int main(){

      float a, b, temp;

      printf("Enter value of a: ");

      scanf("%f",&a);

      printf("Enter value of b: ");

      scanf("%f",&b);

      temp = a;    /* Value of a is stored in variable temp */

      a = b;       /* Value of b is stored in variable a */

      b = temp;    /* Value of temp(which contains initial value of a) is stored in variable b*/

      printf("\nAfter swapping, value of a = %.2f\n", a);

      printf("After swapping, value of b = %.2f", b);

      return 0;

}

Write a program to  Check Whether a Number is Even or Odd?

#include <stdio.h>

int main(){

      int num;

      printf("Enter an integer you want to check: ");

      scanf("%d",&num);

      if((num%2)==0)      /* Checking whether remainder is 0 or not. */

           printf("%d is even.",num);

      else

           printf("%d is odd.",num);

      return 0;

}

Write a program to  Check Whether a Character is Vowel or consonant?

#include <stdio.h>

int main(){

  char c;

  printf("Enter an alphabet: ");

  scanf("%c",&c);

  if(c=='a'||c=='A'||c=='e'||c=='E'||c=='i'||c=='I'||c=='o'||c=='O'||c=='u'||c=='U')

       printf("%c is a vowel.",c);

  else

       printf("%c is a consonant.",c);

  return 0;

}

Check Leap Year?

#include <stdio.h>

int main(){

      int year;

      printf("Enter a year: ");

      scanf("%d",&year);

      if(year%4 == 0)

      {

          if( year%100 == 0) /* Checking for a century year */

          {

              if ( year%400 == 0)

                 printf("%d is a leap year.", year);

              else

                 printf("%d is not a leap year.", year);

          }

          else

             printf("%d is a leap year.", year );

      }

      else

         printf("%d is not a leap year.", year);

      return 0;

}

Calculate Sum of Natural Numbers?

#include <stdio.h>

int main()

{

    int n, count, sum=0;

    printf("Enter an integer: ");

    scanf("%d",&n);

    count=1;

    while(count<=n)       /* while loop terminates if count>n */

    {

        sum+=count;       /* sum=sum+count */

        ++count;

    }

    printf("Sum = %d",sum);

    return 0;

}

Find the Largest Number Among Three Numbers?

#include <stdio.h>

int main(){

      float a, b, c;

      printf("Enter three numbers: ");

      scanf("%f %f %f", &a, &b, &c);

      if(a>=b && a>=c)

         printf("Largest number = %.2f", a);

      if(b>=a && b>=c)

         printf("Largest number = %.2f", b);

      if(c>=a && c>=b)

         printf("Largest number = %.2f", c);

      return 0;

}

Check Character is an alphabet or not?

#include <stdio.h>

int main()

{

    char c;

    printf("Enter a character: ");

    scanf("%c",&c);

    if( (c>='a'&& c<='z') || (c>='A' && c<='Z'))

       printf("%c is an alphabet.",c);

    else

       printf("%c is not an alphabet.",c);

    return 0;

}

Check Whether a Number is Positive or Negative or Zero.

#include <stdio.h>

int main()

{

    float num;

    printf("Enter a number: ");

    scanf("%f",&num);

    if (num<=0)

    {

        if (num==0)

          printf("You entered zero.");

        else

          printf("%.2f is negative.",num);

    }

    else

      printf("%.2f is positive.",num);

    return 0;

}

Generate Multiplication Table?

#include <stdio.h>

int main()

{

    int n, i;

    printf("Enter an integer to find multiplication table: ");

    scanf("%d",&n);

    for(i=1;i<=10;++i)

    {

        printf("%d * %d = %d\n", n, i, n*i);

    }

    return 0;

}

Reverse an Integer?

#include <stdio.h>

int main()

{

  int n, reverse=0, rem;

  printf("Enter an integer: ");

  scanf("%d", &n);

  while(n!=0)

  {

     rem=n%10;

     reverse=reverse*10+rem;

     n/=10;

  }

  printf("Reversed Number = %d",reverse);

  return 0;

}

 Check Palindrome Number?

#include <stdio.h>

int main()

{

  int n, reverse=0, rem,temp;

  printf("Enter an integer: ");

  scanf("%d", &n);

  temp=n;

  while(temp!=0)

  {

     rem=temp%10;

     reverse=reverse*10+rem;

     temp/=10;

  } 

/* Checking if number entered by user and it's reverse number is equal. */ 

  if(reverse==n) 

      printf("%d is a palindrome.",n);

  else

      printf("%d is not a palindrome.",n);

  return 0;

}

 Check Prime Number

#include <stdio.h>

int main()

{

  int n, i, flag=0;

  printf("Enter a positive integer: ");

  scanf("%d",&n);

  for(i=2;i<=n/2;++i)

  {

      if(n%i==0)

      {

          flag=1;

          break;

      }

  }

  if (flag==0)

      printf("%d is a prime number.",n);

  else

      printf("%d is not a prime number.",n);

  return 0;

}

Write to a Sentence to a File?

#include <stdio.h>

#include <stdlib.h>  /* For exit() function */

int main()

{

   char c[1000];

   FILE *fptr;

   fptr=fopen("program.txt","w");

   if(fptr==NULL){

      printf("Error!");

      exit(1);

   }

   printf("Enter a sentence:\n");

   gets(c);

   fprintf(fptr,"%s",c);

   fclose(fptr);

   return 0;

}

Read a String of Text from File

#include <stdio.h>

#include <stdlib.h> /* For exit() function*/

int main()

{

   char c[1000];

   FILE *fptr;

   if ((fptr=fopen("program.txt","r"))==NULL){

       printf("Error! opening file");

       exit(1);         /* Program exits if file pointer returns NULL. */

   }

   fscanf(fptr,"%[^\n]",c);

   printf("Data from file:\n%s",c);

   fclose(fptr);

   return 0;

}

Fibonacci series up to n terms?

#include <stdio.h>

int main()

{

  int count, n, t1=0, t2=1, display=0;

  printf("Enter number of terms: ");

  scanf("%d",&n);

  printf("Fibonacci Series: %d+%d+", t1, t2); /* Displaying first two terms */

  count=2;    /* count=2 because first two terms are already displayed. */

  while (count<n) 

  {

      display=t1+t2;

      t1=t2;

      t2=display;

      ++count;

      printf("%d+",display);

  }

  return 0;

}

 Factorial program in c using recursion?

#include<stdio.h>

 long factorial(int);

 int main()

{

  int n;

  long f;

   printf("Enter an integer to find factorial\n");

  scanf("%d", &n); 

   if (n < 0)

    printf("Negative integers are not allowed.\n");

  else

  {

    f = factorial(n);

    printf("%d! = %ld\n", n, f);

  }

   return 0;

}

 long factorial(int n)

{

  if (n == 0)

    return 1;

  else

    return(n * factorial(n-1));

}

Factorial program in c using for loop

#include <stdio.h>

 int main()

{

  int c, n, fact = 1;

   printf("Enter a number to calculate it's factorial\n");

  scanf("%d", &n);

   for (c = 1; c <= n; c++)

    fact = fact * c;

   printf("Factorial of %d = %d\n", n, fact);

   return 0;

}